1. Field of the Invention
The present invention generally relates to heat treatment apparatuses and more particularly to a heat treatment apparatus which performs an anneal process or a chemical vapor deposition (CVD) process by heating an object to be processed, such as a single crystalline substrate or a glass substrate, with a lamp and a quartz window used for such a heat treatment apparatus. The present invention is suitable for a rapid thermal processing (RTP: Rapid Thermal Processing) used for manufacturing semiconductor devices, such as a memory or an integrated circuit (IC). The rapid thermal processing (RTP) includes rapid thermal annealing (RTA), rapid thermal cleaning (RTC), rapid thermal chemical vapor deposition (RTCVD), rapid thermal oxidization (RTO) and rapid thermal nitriding (RTN).
2. Description of Related Art
Generally, in order to manufacture a semiconductor integrated circuit, various kinds of heat treatment, such as a film deposition process, an anneal process, an oxidization diffusion process, a sputtering process, an etching process and a nitriding processing may be repeatedly performed on a silicon substrate such as a semiconductor wafer a plurality of times.
Since yield rate and quality of semiconductor manufacturing processes can be improved, the RTP technology to rise and drop the temperature of the wafer (object to he processed) has attracted attention. A conventional RTP apparatus generally comprises: a single-wafer chamber (process chamber) for accommodating an object to be processed (for example, a semiconductor wafer, a glass substrate for photograph masks, a glass substrate for a liquid-crystal display or a substrate for optical discs); a reflector (reflective board) arranged at the opposite side of the object to be processed with respect to a quartz window arranged in the interior of the process chamber; and a heating lamp (for example, halogen lamp) arranged at an upper part or above the quartz window, and the lamp.
The reflector is made of aluminum, and gold plating is given to a reflective part thereof. A cooling mechanism such as a cooling pipe is provided so as to prevent temperature breakage of the reflector (for example, exfoliation of gold plating due to a high temperature). The cooling mechanism is provided so as to prevent the reflector from being an obstacle of cooling the object to be processed at the time of cooling. The rapid temperature rising demanded for the RTP technology is dependent on the directivity of the optical irradiation to the object to be processed and the power density of the lamp.
The quartz window may be in the shape of a board, or can be in the form of tube which can accommodate the object to be processed. When maintaining a negative pressure environment in the process chamber by evacuating gasses in the process chamber by a vacuum pump, a thickness of the quartz window is set to, for example, about 30 to 40 mm so as to maintain the pressure difference between the internal pressure and the atmospheric pressure. The quartz window may be formed in a curved shape having a reduced thickness so as to prevent generation of a thermal stress due to temperature difference generated by a temperature rise.
A plurality of halogen lamps are arranged so as to uniformly heat the object to be processed. The reflector reflects the infrared rays irradiated from the halogen lamps toward the object to be processed. The process chamber is typically provided with a gate valve on a sidewall thereof so as to carry in and out the object to be processed. Moreover, a gas supply nozzle, which introduces a process gas used for heat treatment, is connected to the sidewall of the process chamber.
The temperature of the object to be processed affects the quality of process such as, for example, a thickness of a film in a film deposition process, etc. For this reason, it is necessary to know the correct temperature of the object to be processed. In order to attain high-speed heating and high-speed cooling, a temperature measuring device which measures the temperature of the object to be processed is provided in the process chamber. The temperature measuring device may be constituted by a thermocouple. However, since it is necessary to bring the thermocouple into contact with the object to be processed, there is a possibility that the processed body is polluted with the metal which constitutes the thermocouple. Therefore, there is proposed a payro meter as a temperature measuring device which detects an infrared intensity emitted and computes a temperature of an object to be processed from the back side thereof based on the detected infrared intensity. The payro meter computes the temperature of the object to be processed by carrying out a temperature conversion by an emissivity of the object to be processed according to the following expression:
Em(T)=xcex5EBB(T)xe2x80x83xe2x80x83(1)
where, EBB(T) expresses a radiation intensity from a black body having the temperature T; Em(T) expresses a radiation intensity measured from the object to be processed having the temperature T; xcex5 expresses a rate of radiation of the object to be processed.
In operation, the object to be processed is introduced into the process chamber through the gate valve. The peripheral portion of the object to be processed is supported by a holder. At the time of heat treatment, process gases such as nitrogen gas and oxygen gas, are introduced into the process chamber through the gas supply nozzle. On the other hand, the infrared ray irradiated from the halogen lamps is absorbed by the object to be processed, thereby, rising the temperature of the object to be processed.
Recently, a demand for a rapid temperature rise of RTP has been increased so as to achieve a high-quality process of an object to be processed and improve a throughput. For example, there is a demand for increasing a temperature rising rate from 90 degrees/sec to 250 degrees/sec. The temperature rising rate depends on a power density of a lamp and a directivity of light irradiation from the lamp to an object to be processed.
FIG. 1 is an illustration showing an arrangement of a single end lamp and a reflector. As shown in FIG. 1, the directivity with respect to the object to be processed arranged underneath the single end lamp 2 having only one electrode part 3 and the energy efficiency of the lamp 2 are maximized when a degree of an angle xcex1of inclination of a reflector 4 relative to the lamp 2 is set to 45 degrees. However, if the reflector 4 having an inclination angle of 45 degrees is provided around each of a plurality of lamps 2, the lamps cannot be arranged closed to each other, which causes a decrease in the power density. On the other hand, it is considered to achieve a rapid temperature rise as a whole by increasing the lamp density by setting the inclination angle greater than 45 degrees so as to set the inclination angle equal to or close to 90 degrees while sacrificing the directivity and energy efficiency. However, there also is a problem in that the lamp density is prevented from being increased due to need of a cooling mechanism such as a cooling pipe incorporated in the reflector 4 in a two-dimensional arrangement.
It is a general object of the present invention to provide an improved and useful lamp and heat treatment apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a lamp used as a heat source of a heat treatment apparatus which can perform a rapid temperature rise without use of a reflector arranged around the lamp.
In order to achieve the above-mentioned objects, there is provided according one aspect of the present invention a lamp usable as a heat source of a heat treatment apparatus for applying a heat treatment to an object to be processed, the lamp comprising: at least one electrode part to which an electric power is supplied; a light-emitting part connected to the electrode part, the light-emitting part sealing a filament emitting a light; and a high-reflectance film formed on an outer surface of a first part of the light-emitting part so that the high-reflectance film reflects the light emitted from the filament and the reflected light exits from the light-emitting part through a second part of the light-emitting part other than the first part on which the high-reflectance film is formed so as to improve a directivity of the light exiting from the second part of the light-emitting part.
Additionally, there is provided according to another aspect of the present invention a heat treatment apparatus having a process chamber in which a heat treatment is applied to an object to be processed and a plurality of lamps as a heat source for heating the object to be processed, wherein each of the lamps has the same structure as the above mentioned lamp.
The above-mentioned lamp and heat treatment apparatus according to the present invention improves the directivity of the light toward the object to be processed by providing the high-reflectance film on the light-emitting part without using a reflector arranged around each lamp. Additionally, the lamps can be arranged with a high density since there is no need to use a cooling mechanism which is provided in a reflector with a two-dimensional arrangement. Thus, the lamp and the heat treatment apparatus according to the present invention are suitable for a rapid thermal processing (RTP) apparatus.
The lamp according to the present invention may be of a single end type in which the electrode part is connected to one end of the light-emitting part having an elongated tubular shape, and the first part of the light-emitting part may extends in a longitudinal direction of the light-emitting part. Additionally, the light-emitting part may have a straight cylindrical shape having a closed one end as a bottom surface, and the high-reflectance film may be formed on an outer surface of the light-transmitting part other than the bottom surface so that the reflected light exits from the light-emitting part through the bottom part which is arranged to face the object to be processed.
Alternatively, the lamp according to the present invention may be of a double end type in which the electrode part is connected to each opposite end of the light-emitting part having an elongated tubular shape, and the second part of the light-emitting part may face the object to be processed so that the light reflected by the high-reflecting film is directed to the object to be processed.
In the lamp according to the present invention, it is preferable that an outer surface of the first part of the light-emitting part has unevenness so that the high-reflectance film is formed on the outer surface having the unevenness. Additionally, the high-reflectance firm may be formed by gold plating, and a thickness of the high-reflectance film may be about 10 xcexcm. Further, the heat treatment apparatus according to the present invention may further comprise a cooling part for maintaining the first part of the light-emitting part at a temperature not exceeding 500xc2x0 C.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.